It could be an effect of the camera but it looks like your spinnaker luff is too loose. This will cause you to have to sail higher into the wind in order to get wind into the kite and cause it to be more powerful over a wider range of wind angles. With the luff too loose, it will be less powerful on deep angles leaving you slower when you are trying to sail deep to get around a race course efficiently. The soft luff / fuller kite will also carry power over a wider angle of apparent wind which makes it less sensitive to helm corrections as you change your course reacting increased wind pressure and additional boat speed. The fuller kite means you have to steer more dramatically causing lost speed and distance. Tighten the luff and you can sail deeper and make smaller changes in the helm to accommodate the changing wind / boat speed.

When setting up the spinnaker on shore, you should hoist it fully and with the sheet loose, you should grab the luff of the spinnaker making a fist with the luff on the interior of your fist and rotate your hand 45 to 90 degrees before the spinnaker is tight and prevents your hand from rotating further. You want the spinnaker luff to be almost tight when hoisted fully. I bet this will help make the boat easier to sail downwind.